Process for sweetening hydrocarbon fluids



Patented" Sept. 28, 1937 oFFICE mooass Fon SWEETENING n naocma- BONFLUIDS Albert E. Buell, Bartlesvllle, 10km" assignor to PhillipsPetroleum Company, a corporation oi Delaware No Drawing. ApplicationJanuarym, 1937 Serial No. 121,908

8 Claims.

'Ehis application is a continuation in part of my copending application,May 12, 1934.

This invention relates to the refining of hydrocarbon products andparticularly to the'refining of petroleum products containing malodoroussulfur compounds of the mercaptan type. More directly, it relates tosweetening sour petroleum hydrocarbon products by means of a moist solid10 carriers. The invention is of special 'valueand application in thetreatment of light petroleum distillates such as natural gasoline,refinery straight run and crackedgasolines, petroleum solvent naphthas,liquefied petroleum gases, and

the like.

Such unrefined petroleum products contain mercaptans, commonly calledsour elements, which give the oil undesirable odor, and render itcorrosive and unstable. These compounds are customarily removed, oraltered, by the so-called doctor;process, a laborious, cumbersome andvery unecon'omical chemical treatment with alkali plumbite and sulfur.In some instances, e. g., r, natural gasoline, the sweetening reactionhas been accomplished through the use of alkaline hypochloritesolutions, but this method, too, has not proved satisfactory in mostcases. Sometimes the sour" elements seem to be particularly-difficult tosweeten, thereby requiring large quantities of the reagent, and in othercases the treatment'seems to result in the introduction into the oil ofundesirable constituents as bad as those originally present. Still othermethods have been suggested for removal or conversion of the mercaptansbut almost without exception these methods involve numerous treatingsteps which.

demand such close control of the operation that the operating costs areincreased so much as to render such methods uneconomical.

One of the principal objects of the present invention is to provide aprocess for sweetening the mercaptan-bearing oils in'a far moreefficient and inexpensive manner than practiced heretofore. ,5 Anotherobject of the invention is to provide a processior converting themercaptans in the oil to the disulfide form without the production ofand the consequent introduction into the oil 50. of the variousundesirable compounds which are formed as by-products in nearly all ofthe sweetening methods used heretofore.

Still another object of the invention is to prov vide a process whereinthe sweetening reagent is '55 regenerated either continuously orintermittently.

Serial No. 725,405, filed.

reagent comprising copper chloride adsorbed on A further object of theinvention is to provide a process and reagent which isso rapid in itssweetening reaction that the apparatus necessary for this refining stepis very small and inexpensive as compared to that needed for any of themethods suggested heretofore.

-Other objects and novel features and advantages of this invention willbe apparent from the following specification.

I have discovered that a solid treating agent comprising a 'ghly porousor adsorbent material such as fullers earth, charcoal and the like,impregnated .with a concentrated solution of cupric chloride, is anexcellent reagent for rapidly and efficiently sweetening sourhydrocarbon oils. I

have found that during simple filtering of the oils in the liquid stateat ordinary temperatures through a bed of'this reagent the mercaptansare converted to the disulfidesi" .The principal reactions are believedto be shown in the equations:

(1) 2CuCl +4RSI-I--- 2R-SCu+ Cupric Mer- Cuprous chloride captanmercaptide RSS-R+4HC1 v Alkyl Hydrochlodisulflde ric acid (2) 2RSCu+2(IuC1 RSS-R 4CuCl Cuprous Cupric Alkyl Cuprous mercaptide chloridedisulfide chloride In the first step of the reaction, one-half of themercaptan is converted to'the alkyl disulfide and the rest is left ascuprous mercaptide. The latter the'n reacts (as shown in Equation 2)with additional cupric chloride to give alkyl disul-flde and cuprouschloride, On'combining the two equationsintoone, the ultimat'e'reactionis:

Cupric Mer Alkyl chloride captan, disnlfi de 4CuCl 4HCl CuprousHydrochlochloride ric acid Since cuprous chloride and hydrochloric acidcaptan content is high the life of the reagent is quite short.

I have discovered that this spending of the reagent can be prevented andthe activity maintained over long periods even when treating gasolinesof extremely high mercaptan content, e. g.', those of west Texas origin,by dissolving air or an equivalent gas containing free oxygen in thegasoline previous to its passage thru the reagent bed. In this mannerthe cuprous chloride and hydrochloric acid, formed as shown above in thesweetening step, react with the oxygen in the air to give cupricchloride and water.

Theoretically only 8 volumes of air (gas) at 0 C.

- and 750 mm. is required for 100 liquid volumes of gasoline containing0.01% mercaptan sulfur. The quantity of air needed for the west Texasgasolines, some of which contain as high as 0.04% mercaptan sulfur, isstill quite low. I have found by experiment both in laboratory and inplant operations that a sufiicient quantity of air can be dissolved inthe gasoline under the usual conditions of plant operation to keep acupric chloride-fullers earth reagent regenerated. No loss of oil vaporsis encountered in this regenerative process inasmuch as the quantity ofair needed is so small as to cause no appreciable increase in the vaporpressure of the product during treatment. Any gas containing free oxygenand not detrimental to the copper treating reagent, may be used inconjunction with the hydrocarbon fluid so as to maintain the reagent inan active state.

For while it is possible to prepare the reagent in any one of a numberof ways, a preferred way is to spray a concentrated solution containingcupric chloride onto the solid adsorbent material used for the carrier,thereby impregnating the adsorbent with an aqueous solution phasecontaining cupric ions and chloride ions. Fuller's earth is preferred asthe solid adsorbent carrier material, but other materials such ascharcoal, silica gel, alumina, pumice, etc., are suitable. It isunderstood, of course, that' the cupric chloride solution may beprepared not only from the salt itself, but also from other solublecopper salts with suitable soluble alkaline chlorides; copper sulphateand sodium chloride, for example, are a preferred combination. By theterm aqueous solution phase I mean to imply that the interstices orpores of the adsorbent are partly or completely filledwith an aqueoussolution containing copper chloride; obviously the quantity depends onthe natureof-the' selected adsorbent, but, for example,'with 'fullersearth a preferred quantity of solution lies within the rangewhichfinished reagent. i

It is evident-that the 'best sweetening results will produce a contentof'5 to 10% CuClz in the can be obtained by -ha'ving arelatively largevolume of *a compar-atively concentrated solution adsorbed' in thecarrier. However, in order to apply the solution uniformly to thecarrier it is usually desirable to use a somewhat more dilute solutionthan that desired in the finished reagent,

water of solution from the impregnated adsorbent, thus concentrating thesolution. after it has been adsorbed; but, if desired, the volume andconcentration of the solution used for impregnation of a unit quantityof adsorbent may be controlled to give a finished reagent of the desiredcomposition without removal or addition of Water to it before use.

In the operation of the process as stated, hydrogen sulfide if presentis removed by any desired means from the sour gasoline before treatmentwith the above described sweetening reagent. The requisite quantity ofair is then dissolved in the gasoline, preferably using some excess airover the theoretical amount to take care of normal fluctuations inoperation. The air may be added to the stream of sour gasoline flowingto the treater in any suitable manner; the amount may be automaticallycontrolled in proportion'to the flow of gasoline if desired, and the airmay be introduced thru a porous tube or plate to break it up into smallbubbles to insure rapid solution. The gasoline is then contacted withthe reagent, preferably by filtration thru a bed disposed in a suitableclosed treating vessel. Flow rates of 10-20 volumes of gasoline per hourper volume of reagent are generally satisfactory, but higher or lowerrates may be used, depending mainly on the mercaptan content of thegasoline or other hydrocarbon fluid treated.

Under normal conditions of continuous use the reagent has anindefinitely long life, averaging from six to twelve months, or longer.The principal change tending to occur is in the water content. In someinstances this is due to accumulation of water of reaction, or removalof water present in the gasoline by the reagent, resulting in dilutionof the solution with which the carrier is impregnated. In other casesthe gasoline being treated may contain little or no dissolved water,particularly where it has been previously carefully fractionated forremoval of excessively volatile hydrocarbons such as propane, and watersteps, as outlined below, to maintainthe volume within theseandconcentration of the solution limits.

Where, after a considerable period of operafl tion, the reagent hasaccumulated water beyond-,

that originally present, the reagent may be:: ;re'=- stored tosubstantially its original-elfectiueness; by removal of the accumulated.excessl'awatelli this may be done, for example;byvblovqtngcthe reagentbed with air, preferably heated to F. or so; or by removing theireagentIrom-the treating vessel and then zre'movi-ng :the excessmoisture. Under .nocircumstances, however, should the water beremovedtoaipointwhere the aqueous solution phase is destroyed, for it isessential to the conduct of the process covered by this application thatan aqueous phase containing cupric ions and chloride ions b maintainedon the carrier, since without itthe acid formed in the first step of thereaction (Equation 1) is not held by the reagent, and thus it cannot beregenerated, and the treated oil will contain acid and the veryobjectionable copper mercaptide.

By removing accumulated water at intervals, and taking the necessaryprecautions to prevent introduction of water into the reagent by thegasoline, other than reaction water, the life of 5 the sweetening agentmay be considerably prolonged.

Where the tendency is toward the reverse condition, that is, removal ofwater from there- 'agent by gasoline which is not saturated with water,the aqueous'phase may be maintained on the carrier by adding water tothe gasoline before treatment, so that the added water plus that formedin the reaction will balance the water content of the treated gasoline.One convenient way of accomplishing this is by introduction of acontrolled small quantity of steam into the sour gasoline; the condensedsteam is'thoroughly dispersed and dissolved. Insome cases the reagentlife has been prolonged in this way to an indefinite period, comparedwith a period of only a few days without the addition of moisture beforethe reagent became dehydrated to the extent that the sweetening andregenerating reactions would not proceed.

In either case, therefore, whether the reagent tends to accumulate or tolose water, the life may be greatly prolonged by maintaining the aqueoussolution phase with which the adsorbent is impregnated within the limitsspecified; in most cases, however, normal conditions are such that .thesolution concentration remains at substantially its original value, andthe reagent requires attention only at infrequent intervals, as illus-'trated by the following examples:

Example I A very sour west Texas gasoline, containing about 0.05%mercaptan sulfur, is treated by .adding air and then passing it thru abed of about 40 2,000 pounds of sweetening reagent at a flow rate ofabout 15,000 gallons per day. At approximately 100 day intervalsaccumulated water is removed from the reagent by taking the reagent outof the treating vessel and exposing it to the atmosphere until the watercontent is reduced to the original value. Meanwhile, a second treater isused to sweeten the gasoline. This reserve treater contains only 185pounds of sweetening reagent, but can be operated at the 15,000 gallonflow rate for 30 day periods, if desired, before it accumulatessufiicient excess water to prevent sweetening. The reagent wasoriginally prepared by" spraying 15-30 mesh fullers earth with solutioncontaining copper chloride prepared from copper sulfate and an excess ofsodium chloride, to produce a reagent comprising about 75 parts byweight fullers earth, and about 25 parts solution containing about 14%copper and 20% chloride ions.

Example II A sweetening reagent was prepared by uniformly spraying each1,000 pounds of 15-30" mesh fullers earth with about 40 gallons of a (35solution containing about 10% chloride and about 7% cupric copper, madefrom copper sulfate and sodium chloride, and then concentrating theadsorbed solution to about 15% chloride content. The reagent was thenused to treat a Mid-Continent gasoline with alow mercaptan sulfurcontent at a flow rate of about five volumes of gasoline per volume ofreagent per hour, air in the proper proportion being added to thegasoline stream entering the treater. The gasoline was stabilized beforetreating to remove norsorbed in the carrier at approximately itsoriginal Patent is:

mally gaseous hydrocarbons and was substantially" dehydrated by thisfractionation. The dry gasoline removed water from the sweeteningreagent to such an extent that complete sweetening was not obtainedafter several days opera- 5 tion. Steam was then added to the gasolinestieam. before treatment to replace the water removed from the adsorbedsolution phase; the product became completely sweet. Thereafter acontrolled amount of steam was continually 10 added to the gasoline tomaintain the solution at substantially its original concentration, and

the reagent has. continued to be used since.

During the first year of operation about million gallons of gasolinewere treated, with 19,000 15 pounds of reagent present. in the treater.

Example III gallons of reagent prepared as in Example 11 was used tosweeten 10,000 gallons daily of 20 north central Texas natural gasolinefor a period of sixteen months. Normal conditions of operation were.such as to maintain the solution adconcentration, during this period,without addi- 25 tion or removal of water from the reagent by the meansdescribed in the above examples. Cost of the chemicals used inpreparation of the reagent amounted to about 6 mills per 1,000 gallonsof 30 gasoline treated during this period, compared with an average ofabout 16 cents per 1,000 gallons by the method formerly used.

What I claim and desire to secure by Letters 1. A process for sweeteningmercaptan-bearing 35 hydrocarbon oil, comprising contacting said oil, inadmixture with a gas containing free oxygen, with an adsorbent materialimpregnated with a maintained aqueous solution phase containing 40cupric ions and chloride ions.

2. A process for sweetening mercaptan-bearing petroleum oil, comprisingcontacting said oil, in

admixture with air, with an adsorbent material impregnated with amaintained aqueous solution 45 phase containing'cupric ions and chlorideions.

3. A process for sweetening mercaptan-bearing petroleum oil, comprisingadding air to said petroleum oil, and contacting the mixture of said oiland air with a sweetening agent consisting of an 50 adsorbent materialimpregnated with a maintained aqueous solution of a soluble copper saltand a soluble chloride, whereby the said petroleum oil is sweetened andthe sweetening agent is maintained active. 55

4. A process for sweetening mercaptan-bearing gasoline, comprisingcontacting said gasoline, in the presence of a small proportion of air,with a sweetening agent consisting of an adsorbent material impregnatedwith a maintained aqueous 0 solution of a soluble copper salt and asoluble chloride, whereby the said gasoline is sweetened and thesweetening agent is maintained active.

5. A process for sweetening mercaptan-bearing petroleum oil, comprisingadding, air to said oil, 65

through a body of sweetening agent consisting of fullers earthimpregnated with a maintained aqueous solution of a soluble copper saltand a soluble chloride, whereby the said gasoline is sweetened and thesweetening agent is maintained active.

7. A process as in claim 3 in which the soluble copper salt is coppersulfate and the soluble chloride is sodium chloride.

ALBERT E. BUELL.

